In one of the most intriguing subplots of the 2012 GOP nominating contest, the two Minnesota Republicans have begun trading jabs in Iowa over everything from Bachmann's penchant for gaffes to Pawlenty's conservative credentials.

"She has a record for saying things that are off the mark," Pawlenty said Monday in Davenport, where he emphasized his advantage in executive experience. "There is a big difference between talking about things and getting them done."

Pawlenty's swipes came in response to a weekend broadside by Bachmann, who compared him to President Barack Obama on the central complaint of the tea party movement.

"I have fought against irresponsible spending while Gov. Pawlenty was leaving a multibillion-dollar budget mess in Minnesota," said Bachmann, echoing the Democratic critique of the former two-term governor.

The barbs highlight the stakes for both candidates in the first-in-the-nation caucus state.

Even the title of Pawlenty's current RV tour, "Road to Results," seemed destined to put him on a collision course with Bachmann, whose record in Congress he has assailed as "non-existent."

Bachmann, leading in the polls in a state where both need to do well, had kept her powder dry until now, rejecting what she called "negative" politics.

But Pawlenty, trailing badly, began taking regular shots a week ago, portraying Bachmann as someone with "speech capabilities" but little substance to back that up.

With the all-important straw poll in Ames just three weeks away, Bachmann decided to hit back. On Sunday, hours after Pawlenty criticized her in a CNN interview, Bachmann issued a sweeping statement on Pawlenty's record as governor, attacking him for his past praise for Wall Street bailouts, health care mandates and climate change regulations.

"Executive experience is not an asset if it simply means bigger and more intrusive government," said Bachmann, taking aim at the Pawlenty's campaign's core selling point.

Bachmann's haymaker also came days after Pawlenty was one of the few Republican candidates to weigh in on revelations about her chronic migraines, saying the president must be able to "do the job every day, all the time."

Even though Pawlenty later backtracked on his comments about her headaches, the feud continued to escalate between the allies-turned-rivals.

Pawlenty Freedom First political action committee donated $2,400 last year to Bachmann's 2010 U.S. House re-election campaign. But relations turned frosty over the winter when Bachmann began exploring her own presidential bid. Already a national figure as an outspoken tea party champion, Bachmann rapidly eclipsed more than a year of methodical preparation by the lesser-known Pawlenty.

The two, sometimes dubbed the "Minnesota Twins" of the 2012 race, largely avoided public mention of each other for the past several months, each cultivating a separate base of donor support.

But with Iowa looming large in the long-term strategies of both campaigns, it seemed inevitable they would clash.

The day after Bachmann's formal presidential announcement in her native Waterloo, Pawlenty supporter Ron Carey, Bachmann's former chief of staff, penned an opinion piece in the Des Moines Register describing her congressional office as "wildly out of control."

"It is clear to me that while Tim Pawlenty possesses the judgment, the demeanor and the readiness to serve as president," Carey continued, "Michele Bachmann decidedly does not."

Carey, a former chairman of the Minnesota Republican Party, is among the state's GOP luminaries who have sided publicly with Pawlenty. Among others are U.S. Reps. John Kline and Erik Paulsen.

But on Friday at a Des Moines ice rink, Pawlenty found himself in a media scrum fending off speculation that Carey or another Bachmann defector might have been the source of the migraine story, which was leaked anonymously to the conservative Daily Caller website last week.

Pawlenty said he had checked with his "senior staff," and was certain his camp was not involved.

Meanwhile, the war of words went on.

Bachmann, reacting to Pawlenty's continuing attacks on her congressional record, dug up some of the positions of Pawlenty's past, including a 2006 speech as governor when he said, "The era of small government is over."

"That's the same philosophy that, under President Obama, has brought us record deficits, massive unemployment, and an unconstitutional health care plan," Bachmann said in a statement from Cedar Rapids.

Pawlenty spokesman Alex Conant responded that "there is very little difference" between Bachmann and Pawlenty on the issues. Firing back, he added that while Pawlenty was pressing spending cuts on a Democratic-Farmer-Labor Party Legislature in Minnesota, Bachmann "was giving speeches and offering failed amendments, all the while struggling mightily to hold onto the most Republican House seat in the state."